Traffic light colour (5)
(Other definitions for green that I've seen before include "Ecologically correct" , "Environmental - colour" , "conservationist" , "Environment-friendly" , "Eg, avocado, emerald" .)
'traffic light colour' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for amber that I've seen before include "A yellowy resin" , "Warning to traffic" , "Cautionary light" , "Cautionary colour" , "Road warning" .)
(Other definitions for red that I've seen before include "Very angry, seeing this" , "See it and become angry" , "Colour of 1 across" , "- Cross; - admiral" , "Crimson" .)